Recently, developments have been promoted for power assist apparatuses which assist motions of, for example, physically challenged people who have lost their muscle forces and elderly people whose muscle forces have decreased (hereinafter referred to as the “person/people to be assisted”) or which make motions of the people to be assisted instead of those people. These days, a wearable motion assisting apparatus has been proposed which is capable of being worn on a person to be assisted and generating a necessary motive power at any time based on an intention of the person to be assisted (see, for example, Japanese laid-open patent publication No. 2005-253650).
The wearable motion assisting apparatus includes a motion assisting wearing device which is to be worn on an arm or a leg of a person to be assisted. An example of a motion assisting wearing device, which has been proposed, includes: a trunk member which is to be worn on a part near a shoulder; an upper arm member which is coupled to the trunk member via a shoulder joint mechanism having at least one rotation axis and which is to be worn on an upper arm of a wearer; and a forearm member which is coupled to the upper arm member via an elbow joint mechanism having at least one rotation axis and which is to be worn on a forearm of the wearer. Such a motion assisting wearing device provides a rotation of the upper arm member with respect to the trunk member and a rotation of the forearm member with respect to the upper arm member, and provides such rotational movements using a motive power generated by a driving apparatus (actuator) provided in the joint mechanisms. A person who wears the motion assisting wearing device (wearer) can hold a relatively heavy object utilizing the motive power of the driving apparatus.